Add WS subscribe latency monitoring

monitoring/src/main/java/org/thingsboard/monitoring/data/Latencies.java

@@ -17,8 +17,8 @@ package org.thingsboard.monitoring.data;
 
 public class Latencies {
 
-    public static final String WS_UPDATE = "wsUpdate";
     public static final String WS_CONNECT = "wsConnect";
+    public static final String WS_SUBSCRIBE = "wsSubscribe";
     public static final String LOG_IN = "logIn";
 
     public static String request(String key) {

monitoring/src/main/java/org/thingsboard/monitoring/service/BaseMonitoringService.java

@@ -100,7 +100,10 @@ public abstract class BaseMonitoringService<C extends MonitoringConfig<T>, T ext
             reporter.reportLatency(Latencies.LOG_IN, stopWatch.getTime());
 
             try (WsClient wsClient = wsClientFactory.createClient(accessToken)) {
+                stopWatch.start();
                 wsClient.subscribeForTelemetry(devices, TransportHealthChecker.TEST_TELEMETRY_KEY).waitForReply();
+                reporter.reportLatency(Latencies.WS_SUBSCRIBE, stopWatch.getTime());
+
                 for (BaseHealthChecker<C, T> healthChecker : healthCheckers) {
                     check(healthChecker, wsClient);
                 }